Dib Venturelli, Claudio Omar

We study leptonic decays W± → e±e±μ∓ν and W± → μ±μ±e∓ν which would occur at the LHC if there exist sterile neutrinos with masses below MW . We also study ways to discriminate their Majorana or Dirac character, a rather non trivial task, because lepton number conservation cannot be checked due to the missing neutrino in the final state. We find that it is indeed possible to discriminate between Majorana vs. Dirac sterile neutrinos by comparing the production of e±e±μ∓ vs. μ±μ±e∓ if the N-e and N-μ mixings are sufficiently different. Alternatively, one could also distinguish the Majorana vs. Dirac character by studying the energy spectra of the opposite charge lepton, a method that works even for equal N-e and N-μ mixings.

We propose to study the leptonic decays W± → e±e±μ∓ν and W± → μ±μ±e∓ν at the LHC to discover sterile neutrinos with masses below MW , and discriminate their Majorana or Dirac character. These decays are induced by a sterile neutrino N that goes on mass shell in the intermediate state. We find that, even though the final (anti-)neutrino goes undetected and thus lepton number is unchecked, one can distinguish between the Majorana vs. Dirac character of the intermediate sterile neutrino by comparing the production of e±e±μ∓ vs. μ±μ±e∓, provided the N-e and N-μ mixings are different enough. Alternatively, one can also distinguish the Majorana vs. Dirac character by studying the energy spectra of the opposite charge lepton, a method that works even if the N-e and N-μ mixings are equal.